This invention relates to well completion and servicing fluids, and more particularly to well completion and servicing fluids that are noncorrosive, free of solids which are not soluble in hydrochloric acid, and capable of being formulated at densities greater than 22 pounds per gallon.
In the completion and/or servicing of oil and gas wells, it is often desirable to contain the formation pressure by employing a column of fluid in the well. Well completion and servicing fluids may be used during squeezing operations, perforation operations, well shut-ins, gravel packing or other completion operations. Many completion and servicing fluids have been used for this purpose. These include, for example, drilling mud, brine, and solutions of zinc or calcium chlorides or bromides. These fluids have been successful to varying degrees, but are subject to certain disadvantages and limitations. Drilling muds are not completely satisfactory because solids contained in the muds frequently tend to plug the formation. Although solutions of certain inorganic salts tend to be particle-free, there are other difficulties with their use as well-servicing fluids. For example, most inorganic salt solutions commonly used in wells in the Gulf Coast region of the United States are low density fluids having high crystallization temperatures. For instance, sodium chloride-based fluids have a density of up to about 9.8 pounds per gallon (ppg); solutions of calcium chloride have a density of up to about 11.7 ppg; solutions of calcium chloride and zinc chloride have a density of up to about 14.0 ppg; and solutions of CaCl.sub.2 and CaBr.sub.2 have densities of up to about 15.1 ppg.
In recent years, deeper, high-pressure wells have resulted in a need for well-servicing fluids having higher densities than are currently available. This is particularly true of wells in the Gulf of Mexico. There, treatment of high-pressure wells often requires well-servicing fluids having densities in excess of 15 pounds per gallon and crystallization points below about 50.degree. F. Recently, fluids comprised of CaBr.sub.2 and ZnBr.sub.2 have been developed that have a density of from about 15 to 20 ppg. However, these fluids are very expensive and very corrosive.
Thus, there has been a continuing need for well completion and servicing fluids that can be formulated at high densities, such as greater than 15 ppg, but which are not subject to the disadvantages of the presently available fluids.